[a] Prior to May 2012 the Official Bank rate was published to two decimal places but has since been changed to four decimal places for consistency.

[b] On the 16th September 1992, the UK leaves the European Exchange Rate Mechanism. The minimum lending rate was raised to 12%, and planned to be raised to 15% (with effect from 17th September 1992; but never implemented). Please see:
http://www.bankofengland.co.uk/archive/Documents/historicpubs/qb/1992/qb92q4382398.pdf for further explanation of changes implement to the minimum lending rate on "Black Wednesday".